OS1st Size Guide - Performance Foot Sleeve
| X-Small | Small | Medium | Large | X-Large | |
| US (Men's) | 3-5.5 | 6-9.5 | 10-13 | 13.5-15 | |
| US (Women's) | 4 | 4.5-6.5 | 7-10.5 | 11+ |
| X-Small | Small | Medium | Large | X-Large | |
| US (Men's) | 3-5.5 | 6-9.5 | 10-13 | 13.5-15 | |
| US (Women's) | 4 | 4.5-6.5 | 7-10.5 | 11+ |